PROJECT SUMMARY/ABSTRACT Household contact investigation is an evidence-based, WHO-recommended approach to finding undiagnosed patients with tuberculosis (TB) that is now being implemented in high-burden, low-income countries. During the current award period, we have identified major gaps in the delivery of TB contact investigation in Kampala, Uganda; characterized these gaps in behavioral terms; and designed, implemented, and evaluated a theory- informed strategy targeting these gaps in a household-clustered, randomized trial. Unfortunately, the strategy, ?home-based? TB contact investigation, was not effective in increasing either TB evaluation or diagnosis, although contacts and health workers both preferred it. Fidelity of delivery of the intervention's core components ? home HIV and TB testing and results reporting via text messaging ? was low, suggesting a need to refine the models of delivery. Human-Centered Design (HCD) offers a novel approach to improving the fit of interventions to household members using co-creation, rapid prototyping, and iterative testing to identify more engaging delivery solutions. Communities of Practice ? close networks of professionals that form to provide peer support and share tacit knowledge ? are increasingly recognized as resources to promote and sustain quality in health care. Therefore, we propose to collaborate with IDEO.org, a global innovator in Human- Centered Design, to refine the delivery of home-based TB contact investigation. We will also engage lay health workers using Communities of Practice to adapt and sustain delivery of core intervention components. We will then evaluate the refined implementation strategy in a stepped-wedge, cluster-randomized trial in six urban Ugandan communities not involved in the HCD refinements. We will determine if the HCD-refined strategy ? home-based TB contact investigation delivered via lay health worker communities of practice ? improves the quality, yield, and sustainability of household TB contact investigation relative to a standard strategy. Finally, we will carry out a detailed process evaluation with nested mixed-methods studies to assess fidelity/adaptation, sustainability, and their determinants, as well as an economic evaluation (including empirical costing) to determine cost and cost-effectiveness. We will carry out this work with programmatic partners in the real-world environment provided by the Uganda TB Implementation Research Consortium. Our well-established team of investigators has relevant methodological experience (Human-Centered Design, implementation science, biostatistics, mixed-methods, economic evaluation) and content expertise (HIV, TB diagnostics and contact investigation, mobile technology). This research will make a significant contribution to public health by determining if, how, and why novel, patient-centered models for delivering household contact investigation in low-income countries are effective, efficient, sustainable, and cost-effective. We will also produce generalizable knowledge about the value of Human-Centered Design and Communities of Practice as tools and methods for improving fit and delivery of implementation strategies in low-income settings.